Cutting elements for earth-boring tools, earth-boring tools including such cutting elements and related methods

ABSTRACT

Cutting elements, earth-boring drill bits having such cutting elements and related methods are described herein. In some embodiments, a cutting element for an earth-boring tool may include a superabrasive table having a recessed surface in a cutting face thereof and a shaped feature in a substrate at the interface between the superabrasive table and the substrate, the shaped feature corresponding to the recessed surface in the cutting face of the superabrasive table. In further embodiments, a cutting element for an earth-boring tool may comprise a superabrasive table positioned on a substrate, and at least one substantially planar recessed surface in a cutting face of the superabrasive table. In yet additional embodiments, a cutting element for an earth-boring tool may comprise a superabrasive table positioned on a substrate, and at least one non-planar recessed surface in a cutting face of the superabrasive table.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/472,377, filed May 15, 2012, pending, which application claims thebenefit of U.S. Provisional Patent Application Ser. No. 61/535,766,filed Sep. 16, 2011, entitled “Cutting Elements for Earth-Boring Tools,Earth-Boring Tools Including Such Cutting Elements and Related Methods,”the disclosure of each of which is incorporated herein in its entiretyby reference. The subject matter of this application is also related tothe subject matter of U.S. patent application Ser. No. 13/951,173, filedJul. 25, 2013, entitled “Methods of Drilling a Subterranean Bore Hole,”the disclosure of which is incorporated herein in its entirety byreference.

TECHNICAL FIELD

Embodiments of the present disclosure relate to earth-boring tools,cutting elements for such earth-boring tools, and related methods.

BACKGROUND

Wellbores are formed in subterranean formations for various purposesincluding, for example, extraction of oil and gas from the subterraneanformation and extraction of geothermal heat from the subterraneanformation. Wellbores may be formed in a subterranean formation using adrill bit such as, for example, an earth-boring rotary drill bit.Different types of earth-boring rotary drill bits are known in the artincluding, for example, fixed-cutter bits (which are often referred toin the art as “drag” bits), rolling-cutter bits (which are oftenreferred to in the art as “rock” bits), diamond-impregnated bits, andhybrid bits (which may include, for example, both fixed cutters androlling cutters). The drill bit is rotated and advanced into thesubterranean formation. As the drill bit rotates, the cutters orabrasive structures thereof cut, crush, shear, and/or abrade away theformation material to form the wellbore. A diameter of the wellboredrilled by the drill bit may be defined by the cutting structuresdisposed at the largest outer diameter of the drill bit.

The drill bit is coupled, either directly or indirectly, to an end ofwhat is referred to in the art as a “drill string,” which comprises aseries of elongated tubular segments connected end-to-end that extendsinto the wellbore from the surface of the formation. Often various toolsand components, including the drill bit, may be coupled together at thedistal end of the drill string at the bottom of the wellbore beingdrilled. This assembly of tools and components is referred to in the artas a “bottom-hole assembly” (BHA).

The drill bit may be rotated within the wellbore by rotating the drillstring from the surface of the formation, or the drill bit may berotated by coupling the drill bit to a downhole motor, which is alsocoupled to the drill string and disposed proximate the bottom of thewellbore. The downhole motor may comprise, for example, a hydraulicMoineau-type motor having a shaft, to which the drill bit is mounted,that may be caused to rotate by pumping fluid (e.g., drilling mud orfluid) from the surface of the formation down through the center of thedrill string, through the hydraulic motor, out from nozzles in the drillbit, and back up to the surface of the formation through the annularspace between the outer surface of the drill string and the exposedsurface of the formation within the wellbore.

BRIEF SUMMARY

In some embodiments, a cutting element for an earth-boring tool maycomprise a superabrasive table positioned on a substrate, and at leastone substantially planar recessed surface in a cutting face of thesuperabrasive table.

In further embodiments, an earth-boring tool may comprise at least onecutting element. The at least one cutting element may include asuperabrasive table having a recessed surface in a cutting face thereofand a shaped feature in a substrate at the interface between thesuperabrasive table and the substrate, the shaped feature correspondingto the recessed surface in the cutting face of the superabrasive table.

In additional embodiments, an earth-boring tool may comprise at leastone cutting element. The at least one cutting element may include asuperabrasive table positioned on a substrate, and at least onesubstantially planar recessed surface in a cutting face of thesuperabrasive table.

In yet further embodiments, an earth-boring tool may comprise at leastone cutting element. The at least one cutting element may include asuperabrasive table positioned on a substrate; and a plurality ofnon-planar recessed surfaces in a cutting face of the superabrasivetable.

In yet other embodiments, an earth-boring tool may comprise at least oneblade and a plurality of cutting elements. Each cutting element of theplurality of cutting elements may include a superabrasive tablepositioned on a substrate; and at least one recessed surface in acutting face of the superabrasive table. At least one cutting element ofthe plurality of cutting elements is affixed to one or more of a cone, anose, a shoulder, and a gage region of the at least one blade.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming what are regarded as embodiments of the presentdisclosure, various features and advantages of this disclosure may bemore readily ascertained from the following description of exampleembodiments of the disclosure provided with reference to theaccompanying drawings.

FIG. 1 is a perspective view of an earth-boring drill bit includingcutting elements, according to an embodiment of the present disclosure.

FIG. 2 is a partially cut-away side view of a cutting element having arecessed surface in a cutting face according to an embodiment of thepresent disclosure.

FIG. 3 is a perspective view of the cutting element of FIG. 2.

FIG. 4 is a perspective view of a cutting element including a recessedsurface having a generally circular shape, according to an embodiment ofthe present disclosure.

FIG. 5 is a plan view of the cutting element shown in FIG. 4.

FIG. 6 is a plan view of a cutting element including a recessed surfacehaving a generally square shape, according to an embodiment of thepresent disclosure.

FIG. 7 is a plan view of a cutting element including a recessed surfacehaving a generally square shape and a central island or protrusion,according to an embodiment of the present disclosure.

FIG. 8 is a plan view of a cutting element including a recessed surfacehaving a generally pentagonal shape, according to an embodiment of thepresent disclosure.

FIG. 9 is a plan view of a cutting element including a recessed surfacehaving a generally pentagonal shape and a central island or protrusion,according to an embodiment of the present disclosure.

FIG. 10 is a plan view of a cutting element including a recessed surfaceshaped generally as a Reuleaux polygon, according to an embodiment ofthe present disclosure.

FIG. 11 is a perspective view of a cutting element including a pluralityof recessed surfaces having a generally circular shape and arranged in agenerally annular configuration, according to an embodiment of thepresent disclosure.

FIG. 12 is a plan view of the cutting element of FIG. 11.

FIG. 13 is a plan view of a cutting element including a plurality ofrecessed surfaces having a generally circular shape and arranged in agenerally circular configuration, according to an embodiment of thepresent disclosure.

FIG. 14 is a plan view of a cutting element including a plurality ofrecessed surfaces having a generally circular shape and arrangedproximate to an intended cutting edge, according to an embodiment of thepresent disclosure.

FIG. 15 is a plan view of a cutting element including a plurality ofrecessed surfaces having a generally polygonal shape and arranged in agenerally annular configuration, according to an embodiment of thepresent disclosure.

FIG. 16 is a plan view of a cutting element including a plurality ofrecessed surfaces having a generally polygonal shape and arranged in agenerally circular configuration, according to an embodiment of thepresent disclosure.

FIG. 17 is a plan view of a cutting element including a plurality ofrecessed surfaces having a generally polygonal shape and arrangedproximate to an intended cutting edge, according to an embodiment of thepresent disclosure.

FIG. 18 is a perspective view of a cutting element including a pluralityof recessed surfaces having a generally polygonal shape and arranged ina generally annular configuration, according to an embodiment of thepresent disclosure.

FIG. 19 is a cross-sectional side view of a cutting element having three(3) arcuate-shaped cross-sectional recessed surfaces formed in thecutting face of the cutting element, according to an embodiment of thepresent disclosure.

FIG. 20 is a plan view of the cutting element of FIG. 19, illustratingthe annular, concentric, symmetrical orientation of the arcuate-shapedrecessed surfaces, according to an embodiment of the present disclosure.

FIG. 21 is a plan view of a cutting element having six (6)arcuate-shaped cross-sectional recessed surfaces formed in a cuttingface of the cutting element illustrating an annular, concentric,symmetrical orientation of the recessed surfaces, according to anembodiment of the present disclosure.

FIG. 22 is a cross-sectional side view of a portion of a superabrasivetable of a cutting element having three (3) chevron-shapedcross-sectional recessed surfaces formed in a cutting face of thecutting element, according to an embodiment of the present disclosure.

FIG. 23 is a cross-sectional view of a portion of a superabrasive tableof a cutting element having a recessed surface substantially filled witha sacrificial structure, according to an embodiment of the presentdisclosure.

FIG. 24 is a cross-sectional view of a portion of a superabrasive tableof a cutting element with a relatively thin sacrificial structurepositioned over a surface of a recessed surface, according to anembodiment of the present disclosure.

FIG. 25 is a cross-sectional view of a portion of a cutting element witha shaped region at an interface between a superabrasive table and asubstrate corresponding to a shape of a recessed surface in a cuttingface of the superabrasive table, according to an embodiment of thepresent disclosure.

FIG. 26 is a cross-sectional view of a portion of a cutting element witha shaped region at an interface between a superabrasive table and asubstrate corresponding to a shape of a recessed surface in a cuttingface of the superabrasive table positioned radially outward of therecessed surface, according to an embodiment of the present disclosure.

FIG. 27 is a cross-sectional view of a cutting element having a recessedsurface in a cutting face of a superabrasive table interacting with aformation during drilling operations at a relatively low depth-of-cut,according to an embodiment of the present disclosure.

FIG. 28 is a cross-sectional view of a cutting element having a recessedsurface in a cutting face of a superabrasive table interacting with aformation during drilling operations at a relatively high depth-of-cut,according to an embodiment of the present disclosure.

FIG. 29 is a cross-sectional view of a cutting element without arecessed surface in a cutting face of a superabrasive table interactingwith a formation during drilling operations and showing a chipformation.

FIG. 30 is a cross-sectional view of a cutting element with a recessedsurface in a cutting face of a superabrasive table interacting with aformation during drilling operations and showing a fractured formationin granular form, according to an embodiment of the present disclosure.

FIG. 31 is a partial cross-sectional side view of an earth-boring drillbit illustrating selective placement of a plurality of cutting elements,according to an embodiment of the present disclosure.

FIG. 32 is a bottom view of an earth-boring drill bit illustratingselective placement of a plurality of cutting elements, according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

The illustrations presented herein are not actual views of anyparticular earth-boring tool, drill bit, or component of such a tool orbit, but are merely idealized representations which are employed todescribe embodiments of the present disclosure.

As used herein, the term earth-boring tool means and includes any toolused to remove formation material and form a bore (e.g., a wellbore)through the formation by way of the removal of the formation material.Earth-boring tools include, for example, rotary drill bits (e.g.,fixed-cutter or “drag” bits and roller cone or “rock” bits), hybrid bitsincluding both fixed cutters and roller elements, coring bits,percussion bits, bi-center bits, reamers (including expandable reamersand fixed-wing reamers), and other so-called “hole-opening” tools.

As used herein, the term “cutting element” means and includes anyelement of an earth-boring tool that is used to cut or otherwisedisintegrate formation material when the earth-boring tool is used tofaun or enlarge a bore in the formation.

FIG. 1 illustrates an embodiment of an earth-boring tool of the presentdisclosure. The earth-boring tool of FIG. 1 is a fixed-cutter rotarydrill bit 10 having a bit body 11 that includes a plurality of blades 12that project outwardly from the bit body 11 and are separated from oneanother by fluid courses 13. The portions of the fluid courses 13 thatextend along the radial sides (the “gage” areas of the drill bit 10) areoften referred to in the art as “junk slots.” The bit body 11 furtherincludes a generally cylindrical internal fluid plenum, and fluidpassageways (not visible) that extend through the bit body 11 to theexterior surface of the bit body 11. Nozzles 18 may be secured withinthe fluid passageways proximate the exterior surface of the bit body 11for controlling the hydraulics of the drill bit 10 during drilling. Aplurality of cutting elements 20 is mounted to each of the blades 12.

During a drilling operation, the drill bit 10 may be coupled to a drillstring (not shown). As the drill bit 10 is rotated within the wellbore,drilling fluid may be pumped down the drill string, through the internalfluid plenum and fluid passageways within the bit body 11 of the drillbit 10, and out from the drill bit 10 through the nozzles 18. Formationcuttings generated by the cutting elements 20 of the drill bit 10 may becarried with the drilling fluid through the fluid courses 13, around thedrill bit 10, and back up the wellbore through the annular space withinthe wellbore outside the drill string.

FIG. 2 is a side view of a partially cut-away of cutting element 20 ofthe drill bit 10 of FIG. 1. The cutting element 20 includes a cuttingelement substrate 22 having a superabrasive table, such as a diamondtable 24 thereon. The diamond table 24 may comprise a polycrystallinediamond (PCD) material, having a cutting face 26 defined thereon.Superabrasive materials may also be characterized as “superhard”materials and include natural and synthetic diamond, cubic boron nitrideand diamond-like carbon materials. Additionally, an interface 28 may bedefined between the cutting element substrate 22 and diamond table 24.Optionally, the diamond table 24 may have a chamfered edge 30. Thechamfered edge 30 of the diamond table 24 shown in FIG. 2 has a singlechamfer surface 32, although the chamfered edge 30 also may haveadditional chamfer surfaces, and such additional chamfer surfaces may beoriented at chamfer angles that differ from the chamfer angle of thechamfer surface 32, as known in the art. The cutting element substrate22 may have a generally cylindrical shape, as shown in FIG. 2. One ormore arcuate, or “radiused” edges or edge portions may be employed inlieu of, or in addition to, one or more chamfered surfaces at aperipheral edge of the diamond table 24, as known to those of ordinaryskill in the art.

The diamond table 24 may be formed on the cutting element substrate 22,or the diamond table 24 and the cutting element substrate 22 may beseparately formed and subsequently attached together. The cuttingelement substrate 22 may be formed from a material that is relativelyhard and resistant to wear. For example, the cutting element substrate22 may be formed from and include a ceramic-metal composite material(which is often referred to as a “cermet” material). The cutting elementsubstrate 22 may include a cemented carbide material, such as a cementedtungsten carbide material, in which tungsten carbide particles arecemented together in a metallic binder material. The metallic bindermaterial may include, for example, cobalt, nickel, iron, or alloys andmixtures thereof. In some instances, cutting element substrate 22 maycomprise two pieces, the piece immediately supporting the diamond table24 and on which may be formed and bonded to another, longer piece oflike diameter. In any case, the cutting elements 20 may be secured inpockets on blades 12 as depicted in FIG. 1, such as by brazing.

A recessed surface 34 may be defined in the cutting face 26 of thecutting element 20. For example, a generally annular, recessed surface34 may be defined in the cutting face 26 of the cutting element 20, asshown in FIGS. 2 and 3. The recessed surface 34 may be positionedproximate to an edge of the cutting element 20, such as proximate to thechamfer surface 32. In some embodiments, the recessed surface 34 may besubstantially planar and may be substantially parallel to asubstantially planar surface 36 of the cutting face 26. As anon-limiting example, the recessed surface 34 may have a depth D ofbetween about 0.0254 mm and about 2.54 mm relative to substantiallyplanar surfaces 36 of the cutting face 26. The radially outer edge 40 ofthe recessed surface 34 may be positioned a distance X of between about13 mm and about 19 mm from the chamfer surface 32, and the chamfer edge30 may have a width W of between about 0.254 mm and about 0.483 mm. Inone embodiment, the radially outer edge 40 of the recessed surface 34may be positioned a distance X of about 13 mm from the chamfer surface32, and the chamfer edge 30 may have a width W of about 0.254 mm. Inanother embodiment, the radially outer edge 40 of the recessed surface34 may be positioned a distance X of about 16 mm from the chamfersurface 32, and the chamfer edge 30 may have a width W of about 0.406mm. In a further embodiment, the radially outer edge 40 of the recessedsurface 34 may be positioned a distance X of about 19 mm from thechamfer surface 32, and the chamfer edge 30 may have a width W of about0.483 mm. Additionally, at least one angled surface 37 (e.g., angledrelative to the substantially planar cutting surface 36 of the cuttingface 26) may extend between the substantially planar surface 36 of thecutting face 26 and the recessed surface 34.

In additional embodiments, the recessed surface 34 may be defined byshapes other than an annulus. For example, the recessed surface 34 mayhave a generally circular shape, such as shown in FIGS. 4 and 5. Foranother example, the recessed surface 34 may be generally shaped as aregular n-sided polygon, where n may have any value from three (3) toinfinity, whereby n equal to infinity is equivalent to theaforementioned circular embodiment. In one embodiment, as shown in FIGS.6 and 7, the recessed surface 34 may be generally shaped as a square. Inanother embodiment, as shown in FIGS. 8 and 9, the recessed surface 34may be generally shaped as a pentagon. In some embodiments, an island orprotrusion 39 may be positioned at or near a center of the recessedsurface 34, such as shown in FIGS. 2, 3, 7 and 9. The protrusion 39 mayhave an average feature height defined by a plane that is coplanar withthe substantially planar surface 36 of the cutting face 26, as shown inFIG. 3. However, in alternative embodiments, the protrusion 39 may havean average feature height above or below the substantially planarsurface 36 of the cutting face 26. In additional embodiments, therecessed surface 34 may be generally shaped as a Reuleaux polygon (i.e.,a curvilinear polygon built up of circular arcs), such as a Reuleauxtriangle as shown in FIG. 10.

In some embodiments, a cutting element 20 may include a plurality ofrecessed surfaces 34 spaced a distance X from a chamfer surface 32, suchas shown in FIGS. 11-18. In some embodiments, the plurality of recessedsurfaces may comprise a plurality of generally circular shaped recessedsurfaces, such as shown in FIGS. 11-14. For example, a region of thecutting face of the cutting element 20 may have the appearance of adimpled surface of a golf ball. In further embodiments, the plurality ofrecessed surfaces may comprise a plurality of generally polygonal shapedrecessed surfaces, such as hexagon shapes as shown in FIGS. 15-17, orrectangular shapes as shown in FIG. 18. In some embodiments, theplurality of recessed surfaces 34 may be distributed in a generallyannular region of the cutting face of the cutting element 20, such asshown in FIGS. 11, 12, 15 and 18. In further embodiments, the pluralityof recessed surfaces 34 may be distributed in a generally circularregion of the cutting face of the cutting element 20, such as shown inFIGS. 13 and 16. In yet further embodiments, the plurality of recessedsurfaces 34 may be distributed only in a region of the cutting face ofthe cutting element 20 that is near to an intended cutting edge of thecutting element, such as shown in FIGS. 14 and 17.

In some embodiments, as shown in FIGS. 19 through 22, a cutting element20 may include a plurality of nested non-planar recessed surfaces 34,wherein each of the non-planar recessed surfaces is configured to engagethe formation at a specific depth-of-cut. FIGS. 19 and 20 illustrate anembodiment of a cutting element 20 having a plurality of annular,concentric recessed surfaces 34 defined in the cutting face 26 of thecutting element 20. The recessed surfaces 34 are symmetrical about thelongitudinal axis 54 of the cutting element 20. FIG. 19 illustrates across-sectional side view of a cutting element 20 according to such anembodiment. The cutting element 20 includes a cutting element substrate22 having a superabrasive table thereon, such as diamond table 24, aspreviously described. FIG. 19 shows a generally planar interface 28defined between the cutting element substrate 22 and the diamond table24, although any interface geometry is within the scope of the presentdisclosure. Optionally, the diamond table 24 may have a chamfered edge30 and a chamfer surface 32, as previously described herein.

The diamond table 24 may define three non-planar recessed surfaces 34 a,34 b, 34 c formed in the cutting face 26. Each of the recessed surfaces34 a, 34 b, 34 c depicted in FIG. 19 is symmetrical about thelongitudinal axis 54 of the cutting element 20. Each of the recessedsurfaces 34 a, 34 b, 34 c may have an arcuately shaped cross-section or“contour,” and each contour may be of a different radius. For example, afirst, radially outermost recessed surface 34 a may have firstcross-sectional radius R₁; a second recessed surface 34 b may have asecond cross-sectional radius R₂; and a third recessed surface 34 c mayhave a third cross-sectional radius R₃. As shown in FIG. 19, the thirdradius R₃ is greater than both the first radius R₁ and second radius R₂,and the second radius R₂ is greater than the first radius R₁. Moreover,the radially outer edge of the first recessed surface 34 a may bepositioned a first distance X₁ from the chamfer surface 32; the radiallyouter edge of the second recessed surface 34 b may be positioned asecond distance X₂ from the chamfer surface 32; and the radially outeredge of the third recessed surface 34 c may be positioned a thirddistance X₃ from the chamfer surface. As shown in FIG. 19, the thirddistance X₃ is greater than both the first distance X₁ and the seconddistance X₂, and the second distance X₂ is greater than the firstdistance X₁. In this manner, the recessed surfaces 34 a, 34 b, 34 c maybe respectively located to engage formation material at differentrespective depths-of-cut, or alternatively, after the diamond table 24has worn to different extents.

As shown in FIG. 20, the recessed surfaces 34 a, 34 b, 34 c may beannular surfaces concentrically aligned, and each may be symmetricalabout the longitudinal axis 54 (FIG. 19) of the cutting element 20. Itis to be appreciated that the three recessed surfaces 34 a, 34 b, 34 cdepicted in FIGS. 19 and 20 are merely one alternative of any number ofconcentric, annular recessed surfaces which may be formed in the cuttingface 26 of a cutting element 20 according to the present disclosure. Inadditional embodiments, more than three or less than three recessedsurfaces 34 may be formed in the cutting face 26 of the cutting element20. FIG. 21 illustrates a cutting element 20 having more than threerecessed surfaces 34 formed in the cutting face 26 of the cuttingelement 20. By adjusting the parameters of the recessed surfaces 34 a-34c of the cutting element 20 of FIGS. 19 through 21, a plurality ofspecific, tailored performance characteristics can be imparted to thecutting element 20. For example, the radius of each recessed surface 34a-34 c may be set according to a predetermined degree of cuttingaggressivity and efficiency desired for that radial region of thecutting element 20. For example, recessed surfaces with smallerrespective radiuses, such as recessed surface 34 a with radius R₁ ofFIG. 19, may be utilized to manage residual stresses in the diamondtable 24 and increase durability of the cutting element 20.Additionally, recessed surfaces with larger respective radiuses, such asrecessed surface 34 b with radius R₂ of FIG. 19, may be utilized toincrease the aggressivity and efficiency of the cutting element 20.Moreover, the utilization of multiple nested recessed surfaces 34 a-34 cin the cutting face 26 reduces stress concentrations in the cutting face26 and diamond table 24, which may increase the durability and longevityof the cutting element 20. The benefits regarding such reduction instress concentration is explained by author Walter D. Pilkey inPETERSON'S STRESS CONCENTRATION FACTORS (2d ed., Wiley Interscience1997), in Section 2.6.6, on page 71. Thus, by utilizing the concentric,nested configuration of the recessed surfaces 34 a-34 c in the cuttingelement 20 depicted in FIGS. 19 through 21, cutting performancecharacteristics, such as aggressivity and efficiency, may be tailored tooccur at a predetermined depth-of-cut, while balancing durability over agreater portion of the cutting face 26. For example, if a high cuttingaggressivity and efficiency are desired at a shallow depth-of-cut, anannular recessed surface with a large respective radius, such asrecessed surface 34 b with radius R₂ of FIG. 19, may be located at arelatively short radial distance, such as X₁, from the chamfer surface20 of the diamond table 24. Additionally, if residual stress managementis also desired on the diamond table 24 at a greater depth-of-cut, arecessed surface with a smaller respective radius, such as recessedsurface 34 a with radius R₁ of FIG. 19, may be nested radially inward,such as at radial distance X₂ or X₃ of FIG. 19, of the more aggressiverecessed surface.

While FIG. 19 illustrates the recessed surfaces 34 a-34 c as beingsemicircular arcuate shapes, i.e., having one cross-sectional radius, inalternative embodiments, semielliptical cross-sectional shapes may beutilized. Furthermore, in other embodiments, non-planar recessedsurfaces with cross-sectional geometries other than arcuate shapes maybe formed in the cutting face 26 of the cutting element 20. FIG. 22depicts three annular, concentric, chevron-shaped recessed surfaces 34d, 34 e, 34 f formed in the cutting face 26 of the cutting element 20.The cutting element 20 of FIG. 22 may otherwise be configured similarlyto the cutting element 20 of FIGS. 19 and 20. Each of the recessedsurfaces 34 d, 34 e, 34 f depicted in FIG. 22 is symmetrical about thelongitudinal axis 54 of the cutting element 20. Thus, it is to berecognized that the chevron-shaped recessed surfaces are non-planar in athree-dimensional space. Each chevron-shaped recessed surface 34 d, 34e, 34 f may have a symmetrical chevron shape, as depicted in FIG. 22. Inalternative embodiments, non-symmetrical chevron shapes may be utilized.In yet other embodiments, a cutting face 26 may include one or moresymmetrical chevron-shaped recessed surfaces in combination with one ormore non-symmetrical chevron-shaped recessed surfaces. Referring againto FIG. 22, a first, radially outermost, symmetrical, chevron-shapedrecessed surface 34 d may extend to a first depth within the diamondtable 24 at a first angle θ₁ with respect to the planar, longitudinallyouter surface of the cutting face 26. A second, symmetrical,chevron-shaped recessed surface 34 e may extend to a second depth withinthe diamond table 24 at a second angle θ₂ with respect to the planar,longitudinally outer surface of the cutting face 26. A third recessedsurface 34 f may extend to a third depth within the diamond table 24 ata third angle θ₃ with respect to the planar, longitudinally outersurface of the cutting face 26. The angles θ₁, θ₂, θ₃ may be equivalentor unique with respect to one another. For example, FIG. 22 depictsangles θ₂ and θ₃ as being equivalent, and both being greater than θ₁.Moreover, the depth to which the second and third chevron-shapedrecessed surfaces 34 e, 34 f extends from the cutting face 26 into thediamond table 24 is depicted as being equivalent, with both being lessthan the depth to which the first chevron-shaped recessed surface 34 dextends from the cutting face 26 into the diamond table 24. Withcontinued reference to FIG. 22, the radially outer edge of the firstrecessed surface 34 d may be positioned a distance X₁ from the chamfersurface 32; the radially outer edge of the second recessed surface 34 emay be positioned a distance X₂ from the chamfer surface 32; and theradially outer edge of the third recessed surface 34 f may be positioneda distance X₃ from the chamfer surface. As shown in FIG. 22, the thirddistance X₃ is greater than both the first distance X₁ and the seconddistance X₂, and the second distance X₂ is greater than the firstdistance X₁. In this manner, the recessed surfaces 34 d, 34 e, 34 f maybe respectively located to engage formation material at a specificdepth-of-cut, or alternatively, after the diamond table 24 has worn to aspecific extent.

As described above with reference to the arcuate-shaped recessedsurfaces 34 a-34 c of FIGS. 19 through 21, more than three or less thanthree chevron-shaped recessed surfaces 34 d-34 f may be formed in thecutting face 26 of the cutting element 20. Furthermore, as describedabove, by adjusting the parameters of the chevron-shaped recessedsurfaces 34 a-34 c of the cutting element 20 of FIG. 22, includingangles θ₁-θ₃, radial distances X₁-X₃ from the chamfer surface 32, anddepth into the diamond table 24 from the cutting face 26, a plurality ofspecific, tailored performance characteristics, such as durability,aggressivity, and efficiency, can be imparted to the cutting element 20at different radial locations, i.e., depth-of-cut locations, on thecutting face 26. Additionally, any combination of planar and/ornon-planar cross-sectionally shaped recess surfaces 34 a-34 f may beutilized in a single cutting element 20. For example, a combination ofarcuate-shaped recessed surfaces 34 a-34 c, chevron-shaped recessedsurfaces 34 d-34 f, and alternatively shaped recessed surfaces may benested in a concentric pattern on the cutting face 26. Furthermore, inyet additional embodiments, planar and/or non-planar recessed surfaces34, such as the arcuate and chevron cross-sectional recessed surfaces 34a-34 f shown in FIGS. 19 and 22, may be utilized on a cutting face 26 ina non-concentric configuration. Moreover, a nested configuration ofplanar and/or non-planar recessed surfaces 34 a-34 f may be utilized ina non-symmetrical pattern with respect to the longitudinal axis 54(FIGS. 19 and 22) of the cutting element 20. It is to be appreciatedthat a plurality of recessed surfaces 34 of any combination ofcross-sectional shapes, patterns, dimensions, and orientations, asdisclosed above, may be utilized in a single cutting face 26 to impart adesired performance characteristic to a cutting element 20.

The one or more recessed surfaces 34 may be formed in the diamond table24 after the diamond table 24 has been formed, such as by usingelectrical discharge machining (EDM), whereby a desired shape isachieved by using electrical discharges from an electrode (not shown).In some embodiments, the diamond table 24 may be moved relative anelectrode having a shape of a desired cross-section of the recessedsurface 34 (and/or the electrode may be moved along a desired pathrelative to the diamond table 24) to form the recessed surface 34 (FIG.3). For example, an electrode having a polygonal shape may be loweredinto the cutting face 26 of the diamond table 24, and then the diamondtable 24 may be rotated to form a recessed surface 34 comprising apolygonal groove following an annular path. In additional embodiments,one or more electrode dies having a negative shape of the desiredrecessed surface or surfaces 34 (i.e., one or more protrusions), may besunk into the cutting face 26 of the diamond table 24 to form one ormore recessed surfaces 34.

In some embodiments, the one or more recessed surfaces 34 in the diamondtable 24 may include one or more sacrificial structures 42 positionedtherein. For example, one or more sacrificial structures 42 maysubstantially fill the area over the one or more recessed surfaces 34 inthe diamond table 24, such that a surface 44 of each sacrificialstructure 42 may be substantially aligned and coplanar with theadjacent, substantially planar surfaces 36 of the cutting face 26 of thediamond table 24, as shown in FIG. 23. In another example, eachsacrificial structure 42 may be a relatively thin material layerpositioned over the recessed surface 34, as shown in FIG. 24. In someembodiments, each sacrificial structure 42 may be comprised of amaterial that is softer than the diamond table 24, or that is otherwisemore susceptible to wear than the diamond table 24, such as one or moreof a ceramic, a cermet and a refractory metal. For example, the materialof each sacrificial structure 42 may be one or more of tungsten carbide,aluminum oxide, tungsten, niobium, tantalum, hafnium, molybdenum, andcarbides formed therefrom.

In such embodiments, the recessed surface 34 may be formed into thediamond table 24 during the formation of the diamond table 24. Forexample, each sacrificial structure 42 may be positioned within a mold(not shown) and powdered precursor material comprising diamond particlesmay be positioned over (e.g., around) each sacrificial structure 42.Then, the powdered precursor material may be compacted and sintered inthe presence of a catalyst mixed with the diamond particles or sweptfrom an adjacent substrate as known in the art to form the diamond table24, with each sacrificial structure 42 forming a corresponding recessedsurface 34 in the diamond table 24. Each sacrificial structure 42, or aportion thereof, may then be removed, such as by sandblasting,machining, acid leaching or another process, or each sacrificialstructure 42, or a portion thereof, may remain positioned in eachcorresponding recessed surface 34 to be removed by the formation duringdrilling operations. Additionally, for embodiments wherein eachsacrificial structure 42, or a portion thereof, may then be removed,such as by sandblasting, machining, acid leaching or another process,the diamond table 24 may be machined, such as by an EDM process, to afinal geometry.

In further embodiments, a powder preform, such as diamond comprisingpowder contained in a cylindrical niobium cup, may be positionedadjacent a shaped mold, such as a mold having a shaped protrusion,during at least a portion of the sintering process. For example, thepowder preform may be positioned adjacent the shaped mold (not shown)during a high-pressure/high-temperature (HPHT) process and a shapeimparted by the shaped mold may be retained throughout a sintering cycleto form a recessed surface 34 in the diamond table 24. In furtherembodiments, the shape imparted by the mold may be near a desired netshape of the one or more recessed surfaces 34, and the final shape ofthe one or more recessed surfaces 34 may be machined, such as by an EDMprocess, to a final geometry.

Optionally, the catalyst material may be removed from the hardpolycrystalline material of the diamond table 24 after the HPHT process,as known in the art. For example, a leaching process may be used toremove catalyst material from interstitial spaces between theinter-bonded grains of the hard polycrystalline material of the diamondtable 24. By way of example and not limitation, the hard polycrystallinematerial may be leached using a leaching agent and process such as thosedescribed more fully in, for example, U.S. Pat. No. 5,127,923 to Buntinget al. (issued Jul. 7, 1992), and U.S. Pat. No. 4,224,380 to Bovenkerket al. (issued Sep. 23, 1980), the disclosure of each of which patent isincorporated herein in its entirety by this reference. Specifically,aqua regia (a mixture of concentrated nitric acid (HNO₃) andconcentrated hydrochloric acid (HCl)) may be used to at leastsubstantially remove catalyst material from the interstitial spacesbetween the inter-bonded grains in the hard polycrystalline material ofthe diamond table 24. It is also known to use boiling hydrochloric acid(HCl) and boiling hydrofluoric acid (HF) as leaching agents. Oneparticularly suitable leaching agent is hydrochloric acid (HCl) at atemperature of above 110° C., which may be provided in contact with thehard polycrystalline material of the diamond table 24 for a period ofabout two hours to about 60 hours, depending upon the size of the bodycomprising the hard polycrystalline material. After leaching the hardpolycrystalline material, the interstitial spaces between theinter-bonded grains within the hard polycrystalline material may be atleast substantially free of catalyst material used to catalyze formationof inter-granular bonds between the grains in the hard polycrystallinematerial. In some embodiments, leaching may be selectively applied tospecific regions of the diamond table 24, and not to other regions. Forexample, in some embodiments, a mask may be applied to a region of thediamond table 24, such as one or more recessed surfaces 34 or a regionof a recessed surface 34 in the diamond table 24, and only the unmaskedregions may be leached.

Additionally, an outer surface of the diamond table 24 may be physicallymodified, such as by polishing to a smooth or mirrored finish. Forexample, an outer surface of the diamond table 24 may have a reducedsurface roughness, such as described in U.S. Pat. No. 6,145,608, whichissued on Nov. 14, 2000 to Lund et al., and is assigned to the assigneeof the present application; U.S. Pat. No. 5,653,300, which issued Aug.5, 1997 to Lund et al., and is assigned to the assignee of the presentapplication; and U.S. Pat. No. 5,447,208, which issued Sep. 5, 1995 toLund et al., and is assigned to the assignee of the present application,the disclosure of each of which is incorporated herein in its entiretyby this reference.

In conventional PDC cutting elements, a cutting face or leading face ofPDC might be lapped to a surface finish of 20 μin. (about 0.508 μm) to40 μin. (about 1.02 μm) root mean square RMS (all surface finishesreferenced herein being RMS), which is relatively smooth to the touchand visually planar (if the cutting face is itself flat), but whichincludes a number of surface anomalies and exhibits a degree ofroughness which is readily visible to one even under very low powermagnification, such as a 10× jeweler's loupe. However, an exteriorsurface of the diamond table 24 may be treated to have a greatly reducedsurface roughness. As a non-limiting example, an exterior surface of thediamond table 24 may be polished a surface roughness of about 0.5 μin.(about 0.0127 μm) RMS.

In some embodiments, the surface roughness of a surface of the diamondtable 24 may be reduced by lapping of the cutting face 26 onconventional cast iron laps known in the art by using progressivelysmaller diamond grit suspended in a glycol, glycerine or other suitablecarrier liquid. The lapping may be conducted as a three-step processcommencing with a 70-micron grit, progressing to a 40-micron grit andthen to a grit of about 1 to 3 microns in size. In contrast, standardlapping techniques for a PDC cutting element, which may follow aninitial electrodischarge grinding of the cutting face, finish lapping inone step with 70-micron grit. By way of comparison of grit size,70-micron grit is of the consistency of fine sand or crystallinematerial, while 1 to 3 micron grit is similar in consistency to powderedsugar.

In additional embodiments, the surface roughness of a surface of thediamond table 24 may be reduced by placing the surface in contact with adry, rotating diamond wheel. For example, the Winter RB778 resin bondeddiamond wheel, offered by Ernst Winter & Son, Inc., of Travelers Rest,S.C., may be utilized. It may be important that the wheel be cooled asthe diamond wheel is of resin-bonded construction. Elevated temperaturesmay result in the destruction of the wheel. The nature of the polishingprocess may require that the abrasive surface be kept dry. However, thewheel may be moistened with water at the start of the polishing processto reduce drag and facilitate proper orientation of the diamond table 24against the wheel. In addition, a temperature range wherein polishingmay be effected may be between about 140° F. (about 60° C.) and about220° F. (about 104° C.). While specific polishers employed may rotate atabout 3500 rpm, it is believed that a range between about 3000 rpm andabout 5000 rpm would likely be adequate. About 2 lb. force (about 0.9Kg) to about 8 lb. force (about 3.6 Kg) may be applied to the diamondtable 24 against the wheel. As noted, the finish of an exterior surfaceof the diamond table 24 may be smoothed to about 0.5 μm. (about 0.0127μm) RMS, or less, surface finish roughness approaching a true “mirror”finish. It may take about fifty minutes to about an hour of polishingwith the aforementioned diamond wheel to achieve this finish on asurface of a one-half inch (about 1.27 cm) diameter diamond table 24,and about one and one-half to about two hours for a nominalthree-quarter inch (about 1.905 cm) diameter diamond table 24. This samemethod described for polishing a face of the diamond table 24 may alsobe applied to polish the chamfer 32, as well as the side of the diamondtable 24. To polish such surfaces, the diamond table 24, held by thesubstrate 22, is disposed at the desired angle to the rotating wheel.The cutting element 20 may then be rotated about an axis of symmetry tosmooth and polish the chamfer 32 or other side areas of the diamondtable 24. Thus, one could smooth and polish a curved, ridged, waved orother cutting face of a diamond table 24 to remove and reduce both largeand small asperities, resulting in a mirror finish cutting face, whichnonetheless is not flat in the absolute sense.

The cutting element cutting surfaces (cutting face, chamfer, side, etc.)may be polished by other methods, such as ion beams or chemicals,although the inherently inert chemical nature of diamond may make thelatter approach somewhat difficult for diamond. The cutting elementsurfaces may also be polished by the use of lasers, as described inUnited States Patent Publication No. 2009/0114628, to DiGiovanni, whichwas published May 7, 2009, the entire disclosure of which isincorporated herein in its entirety by this reference.

While an industry-standard PDC or other superhard cutting element mayhave a lapped surface finish on the cutting face with irregularities orroughness (measured vertically from the surface) on the order of 20 μin.(about 0.508 μm) to 40 μin. (about 1.02 μm) RMS, as a result of theabove-described polishing, some embodiments may have a diamond table 24surface roughness between about 0.3 μin. RMS and about 0.5 μin. (about0.0127 μm) RMS. Additional embodiments may have a diamond table 24surface roughness between about 0.4 μin. (about 0.0102 μm) RMS and about0.6 μin. (about 0.0152 μm) RMS. In yet additional embodiments, thediamond table 24 may have a surface roughness less than about 10 μin.(about 0.254 μm) RMS. In further embodiments, the diamond table 24 mayhave a surface roughness less than about 2 μin. (about 0.0508 μm) RMS.In yet further embodiments, the diamond table 24 may have a surfaceroughness less than about 0.5 μin. (about 0.0127 μm) RMS, approaching atrue “mirror” finish. In yet further additional embodiments, the diamondtable 24 may have a surface roughness less than about 0.1 μin. (about0.00254 μm). The foregoing surface roughness measurements of the diamondtable 24 may be measured using a calibrated HOMMEL® America Model T-4000diamond stylus profilometer contacting the surface of the diamond table24.

In view of the foregoing, selected surfaces of the diamond table 24 maybe polished or otherwise smoothed to have a reduced surface roughness.In some embodiments, the substantially planar surfaces 36 of the cuttingface 26 may have a reduced surface roughness. In further embodiments,the recessed surface(s) 34 may have a reduced surface roughness. In yetfurther embodiments, the entire cutting face 26 of the diamond table 24may have a reduced surface roughness. In additional embodiments, thechamfer 32 and/or other side surfaces of the diamond table 24 may have areduced surface roughness. In yet additional embodiments, all of theexposed surfaces of the diamond table 24 may have a reduced surfaceroughness.

Referring now to FIG. 28, drilling forces caused by interaction betweena formation 56 and the cutting element 20 may be exacerbated by stressconcentrations within the diamond table 24 above that of an otherwisesimilar PDC cutter without a recessed surface feature 34. In view ofthis, a shape of the interface 28 between the diamond table 24 and thesubstrate 22 of the cutting element 20 may be configured to effectivelydistribute stresses caused by cutting forces, to improve the structuralintegrity of the cutting element 20. For example, a shaped region 48corresponding to a shape of the one or more recessed surfaces 34 in thecutting face 26 of diamond table 24 may define a region of the interface28, such as shown in FIGS. 25 and 26. In some embodiments, the shapedregion 48 of the interface 28 may be defined by a recessed surface 50 inthe substrate 22 and a protrusion 52 (FIGS. 25 and 26) of the diamondtable 24 at the interface 28. In view of this, the shaped region 48 ofthe interface 28 may provide a generally uniform thickness of thediamond table 24. In some embodiments, the shaped region 48 of theinterface 28 corresponding to the one or more recessed surfaces 34 inthe diamond table 24 may be positioned directly, longitudinally, belowthe one or more recessed surfaces 34 in the diamond table 24, as shownin FIG. 25. In further embodiments, at least a portion of the shapedregion 48 of the interface 28 corresponding to the one or more recessedsurfaces 34 in the diamond table 24 may underlie the one or morerecessed surfaces 34 at a position radially inward of the one or morerecessed surfaces 34 relative to a longitudinal axis 54 (FIG. 2) of thecutting element 20. In additional embodiments, at least a portion of theshaped region 48 of the interface 28 corresponding to the one or morerecessed surfaces 34 in the diamond table 24 may underlie the one ormore recessed surfaces 34 at a position radially outward of the one ormore recessed surfaces 34 relative to a longitudinal axis 54 (FIG. 2) ofthe cutting element 20, as shown in FIG. 26. Such a configuration mayaccount for a projected direction of travel of the cutting element 20relative to a formation (as indicated by the dashed lines in FIG. 26),as this may correspond to a primary general direction of cutting forcesapplied to the cutting element 20 during drilling operations. In otherwords, the shaped region of the interface 28 may be sized, shaped andpositioned to reduce stress concentrations, and/or to provide sufficientstructural strength to withstand anticipated stress concentrations, thatmay result from drilling operations. Furthermore, the diamond layeringcomposition of the diamond table 24 may be tailored in the shaped regionof the interface 28 to compensate for residual stresses and provide atailored material property of the diamond table 24, such as a tailoredstrength and toughness, in the shaped region of the interface 28.

In some embodiments, a depth-of-cut limiting feature on an earth-boringtool may be positioned to inhibit interaction between an uncut earthformation and one or more recessed surfaces 34 in the cutting face 26 ofthe diamond table 24 during earth-boring operations. For example, thedepth-of-cut limiting feature on an earth-boring tool may be one or moreof an outer surface of a blade 12 of the drill bit 10 shown in FIG. 1and a bearing block feature as described in U.S. patent application Ser.No. 12/766,988, filed Apr. 26, 2010, for “BEARING BLOCKS FOR DRILL BITS,DRILL BIT ASSEMBLIES INCLUDING BEARING BLOCKS AND RELATED METHODS,” thedisclosure of which is incorporated herein in its entirety by thisreference. For example, the depth-of-cut limiting feature may bepositioned to be aligned with a radially outer edge of a recessedsurface 34 in the cutting face 26 of the diamond table 24. In view ofthis, uncut formation may be prevented from contact with the recessedsurface 34 during drilling operations, such that the planar surface 36of the cutting face 26 and the chamfer surface 32, positioned radiallyoutward (relative to a primary axis of the cutting element 20) of therecessed surface 34 may interact with the uncut formation 56.

In operation at relatively small depths of cut, the uncut formation 56may interact only with the chamfer surface 32 of the cutting element 20,as shown in FIG. 27. At greater depths of cut, the uncut formation 56may interact with the planar surface 36 of the cutting face 26 of thecutting element, as shown in FIG. 28. In view of this, at relatively lowdepths of cut, wherein the uncut formation 56 interacts only with thechamfer surface 32 of the cutting element 20, the cutting element 20 mayexhibit a relatively high effective backrack angle al (FIG. 27). Atrelatively high depths of cut, wherein the uncut formation 56 interactswith the planar surface 36 of the cutting face 26 of the cutting element20, the cutting element 20 may exhibit a relatively low effectivebackrack angle α2 (FIG. 28).

In view of the foregoing, at least one recessed surface 34 in thecutting face 26 of a cutting element 20 may be positioned and configuredto inhibit or reduce the impaction of cuttings removed from a formation56 from compacting together at the cutting face and forming cohesivestructures (i.e., chips). As shown in FIG. 29, when a cutting element 60with a substantially planar cutting face 62 is pushed through an uncutformation 64, the uncut formation 64 fractures and may then besubstantially immediately compacted into the cutting face 62 of thecutting element 60, due to the forward movement of the cutting element60 relative to the formation 64. In view of this, the pieces offractured formation 64 that impact the cutting face 62 of the cuttingelement 60 may become compressed together, forming a cohesive structure66 known generally in the art as a “chip.” However, when a cuttingelement 20 having at least one recessed surface 34, as described herein,in the cutting face 26 positioned just radially inward of the cuttingedge at a sufficient depth is pushed through an uncut formation 70, asshown in FIG. 30, granular pieces 72 of fractured formation 70 may beinhibited or prevented from impacting the cutting element 20 afterfracturing. As a result, the granular pieces 72 of fractured formation70 may not compress together sufficiently to form cohesive structures ofany substantial size and may be carried away by drilling fluid asgranular pieces 72 in discrete particulate form.

In light of this, the work required to penetrate a formation with anearth-boring tool comprising cutting elements 20 with at least onerecessed surface 34 as described herein may be relatively low, as workthat would ordinarily expended by cutting elements compressing afractured formation to form chips may not be required. Furthermore,problems such as balling associated with cuttings or chips sticking to abit face may be prevented or inhibited by utilizing cutting elements 20with at least one recessed surface 34 as described herein, as thefractured formation in granular or particulate form may be readilycarried away from a bit face by drilling fluid.

Performance factors, such as efficiency, aggressivity, and durability,of an earth-boring tool comprising cutting elements 20 with at least onerecessed surface 34 as described herein may be tailored and balanced bystrategic placement of such cutting elements 20 at on the tool. Cuttingelements 20 configured with one or more recessed surfaces 34, asdescribed herein, may exhibit more aggressive and efficient cuttingperformance relative to conventional PDC cutting elements, albeit at theexpense of less durability compared to conventional PCS cuttingelements. Thus, performance of the cutting elements 20 may be furthertailored for specific subterranean formations, such as, by way ofnon-limiting examples, horizontal shales or shaly sands. When harder ormore interbedded formations are to be encountered, the tool design mightretain a larger selection of conventional PDC cutters in the highdepth-of-cut regions of the tool, while using the cutting elements 20,as described herein, in the lower depth-of-cut regions. FIG. 31 is asimple partial cross-sectional view illustrating an embodiment of anearth-boring tool utilizing selective placement of the cutting elements20 of the present disclosure. For illustrative purposes, theearth-boring tool of FIG. 31 is the fixed-cutter rotary drill bit 10 ofFIG. 1, configured as previously described, although it is to berecognized that the selective placement embodiments disclosed herein maybe incorporated on other earth-boring tools, such as reamers,hole-openers, casing bits, core bits, or other earth-boring tools.

As shown in FIG. 31, the drill bit 10 includes a plurality of cuttingelements mounted to each blade 12 of the drill bit 10. Moreover, asunderstood in the art, a profile of a drill bit 10, configured as shownin FIG. 31, may comprise a cone region 74, a nose region 76, a shoulderregion 78, and a gage region 80. Cutting elements located in therespective cone and nose regions 74, 76 of a blade 12 may be exposed toa greater depth-of-cut in formation material relative to cuttingelements located in other regions of the blade 12, but may be subjectedto a lesser work rate than in other regions of the blade 12. Conversely,cutting elements 20 located in the shoulder region 78 of the blade 12may be exposed to a higher work rate, but a lesser depth-of-cut, thancutting elements 20 in other regions of the blade 12. It is to beappreciated that cutting elements 20 having one or more recessedsurfaces 34, as described previously, may be selectively located atspecific regions of the blade 12 to optimize one or more desiredperformance characteristics. As shown in FIG. 31, cutting elements 20,as described herein, may be selectively located in the cone region 74and the nose region 76, and may be configured with one or more recessedsurfaces 34 tailored for specific high depth-of cut performancecharacteristics. Additionally, cutting elements 20, as described herein,may be selectively located in the shoulder region 78 of the blade 12,and may be configured with one or more recessed surfaces 34 tailored forspecific high work rate performance characteristics. The gage region 80of the blade 12 may be fitted with conventional PDC cutting elements. Inadditional embodiments (not shown), cutting elements 20 having one ormore recessed surfaces 34, as described herein, may be selectivelylocated in only one of the cone region 74, nose region 76, shoulderregion 78, or gage region 80, while conventional PDC cutting elementsmay be located in the remaining regions. In yet other embodiments,cutting elements 20 having one or more recessed surfaces 34, asdescribed herein, may be selectively located in any combination of thecone region 74, nose region 76, shoulder region 78, or gage region 80,with conventional PDC cutting elements located in the remaining regionsof the blade 12.

Additionally, referring to FIG. 32, cutting elements 20 having one ormore recessed surfaces 34, as described herein, may be selectivelylocated on one or more blades 12 of the drill bit 10. As shown in FIG.32, a drill bit 10 may be configured with cutting elements 20, asdescribed herein, on alternating blades 12 a-12 c of the drill bit 10,while the remaining blades 12 may be fitted with conventional PDCcutting elements. Benefits of such placement may include, among others,an optimal balance of the aggressivity, stability and steerablity of thedrill bit 10. It is to be appreciated that in further embodiments,cutting elements, such as cutting elements 20 described herein, may beselectively placed on specific blades and on specific regions of eachspecific blade, as described previously, to further tailor performancecharacteristics of the drill bit 10.

Although the foregoing description contains many specifics, these arenot to be construed as limiting the scope of the present disclosure, butmerely as providing certain example embodiments. Similarly, otherembodiments of the disclosure may be devised that are within the scopeof the present disclosure. For example, features described herein withreference to one embodiment may also be combined with features of otherembodiments described herein. The scope of the disclosure is, therefore,indicated and limited only by the appended claims and their legalequivalents, rather than by the foregoing description. All additions,deletions, and modifications to the disclosure, as disclosed herein,which fall within the meaning and scope of the claims, are encompassedby the present disclosure.

What is claimed is:
 1. An earth-boring tool, comprising: a body having aface, the face defining a profile, the profile including at least tworegions; a plurality of cutting elements located on the face, theplurality of cutting elements occupying each of the at least tworegions, at least one cutting element of the plurality of cuttingelements comprising: a substrate; a superabrasive table positioned onthe substrate; and at least one recessed surface in a cutting face ofthe superabrasive table; the at least one cutting element located in oneof the at least two regions; and wherein at least others of theplurality of cutting elements have planar cutting faces without anyrecessed surfaces.
 2. The earth-boring tool of claim 1, wherein the atleast one recessed surface is configured to reduce stress concentrationsin the superabrasive table of the at least one cutting element whenformation material contacts the cutting face within the at least onerecessed surface.
 3. The earth-boring tool of claim 1, wherein the atleast one cutting element is located in a cone region of the at leasttwo regions.
 4. The earth-boring tool of claim 1, wherein the at leastone cutting element is located in a nose region of the at least tworegions.
 5. The earth-boring tool of claim 1, wherein the at least onecutting element is located in a shoulder region of the at least tworegions.
 6. The earth-boring tool of claim 1, wherein the at least onecutting element is located in a gage region of the at least two regions.7. The earth-boring tool of claim 1, wherein each cutting element of theplurality of cutting elements located in the one of the at least tworegions occupied by the at least one cutting element is configuredsimilarly to the at least one cutting element.
 8. The earth-boring toolof claim 7, wherein: the at least one cutting element is a first cuttingelement; a second cutting element of the plurality of cutting elementscomprises: a second substrate; a second superabrasive table positionedon the second substrate; and at least a second recessed surface in asecond cutting face of the second superabrasive table, the at least asecond recessed surface being configured differently the at least onerecessed surface of the first cutting element, and the second cuttingelement being located in one of the at least two regions that is notoccupied by the first cutting element; and each cutting element of theplurality of cutting elements located in the same region of the profileof the face as the second cutting element is configured similarly to thesecond cutting element.
 9. The earth-boring tool of claim 8, wherein thefirst cutting element is located in a nose region of the at least tworegions, and the second cutting element is located in a shoulder regionof the at least two regions.
 10. The earth-boring tool of claim 1,wherein the at least one recessed surface defines one of an arcuate anda chevron cross-sectional shape in the superabrasive table.
 11. Theearth-boring tool of claim 1, wherein a rake angle of the cutting facewithin the at least one recessed surface is different than a rake angleof the cutting face outside of the at least one recessed surface. 12.The earth-boring tool of claim 11, further comprising a depth-of-cutlimiting feature positioned on the earth-boring tool to causeinteraction between uncut earth formation and the at least one recessedsurface in the cutting face of the at least one cutting element duringearth boring operations.
 13. The earth-boring tool of claim 1, whereinthe at least one recessed surface comprises a plurality of recessedsurfaces, the plurality of recessed surfaces being concentricallyaligned.
 14. The earth-boring tool of claim 13, wherein each recessedsurface of the plurality of recessed surfaces defines a cross-sectionalshape different than a cross-sectional shape of each other of theplurality of recessed surfaces.
 15. The earth-boring tool of claim 1,wherein the superabrasive table comprises a surface having a surfaceroughness less than about 10 μin. RMS.
 16. A method of forming anearth-boring tool, the method comprising: providing a body having aface, the face including a plurality of blades, each blade of theplurality of blades defining a profile including at least two regions;selecting at least one cutting element of a plurality of cuttingelements to include: a substrate; a superabrasive table positioned onthe substrate; and at least one recessed surface in a cutting face ofthe superabrasive table; selecting others of the plurality of cuttingelements to have planar cutting faces without any recessed surfaces inthe cutting faces; attaching the at least one cutting element in one ofthe at least two regions; and attaching the others of the plurality ofcutting elements in the at least two regions.
 17. The method of claim16, wherein the at least one cutting element is a first cutting element,the method further comprising: attaching a second cutting element to theprofile of the at least one blade in one of the at least two regionsthat is not occupied by the first cutting element, the second cuttingelement comprising: a second substrate; a second superabrasive tablepositioned on the second substrate; and at least a second recessedsurface in a second cutting face of the second superabrasive table, theat least a second recessed surface being configured differently the atleast one recessed surface of the first cutting element.
 18. The methodof claim 16, wherein the at least one cutting element is a first cuttingelement, the method further comprising: attaching a second cuttingelement to a second blade of the plurality of blades in one of the atleast two regions, the second cutting element comprising: a secondsubstrate; a second superabrasive table positioned on the secondsubstrate; and at least a second recessed surface in a second cuttingface of the second superabrasive table, the at least a second recessedsurface being configured differently the at least one recessed surfaceof the first cutting element.
 19. The method of claim 18, whereinattaching the second cutting element to the second blade of theplurality of blades further comprises attaching the second cuttingelement to the same region of the profile of the second blade as theregion of the profile of the first blade to which the first cuttingelement was attached.
 20. The method of claim 18, wherein attaching thesecond cutting element to the second blade of the plurality of bladesfurther comprises attaching the second cutting element to a region ofthe profile of the second blade different than the region of the profileof the first blade to which the first cutting element was attached.